I feel like there's no need for a backstory being that mAgority of general audience knows what it is, i really feel Thanos arc won't happen in the Avengers until the third film..I feel there big event in 2018 is going to be the infinity gauntlet

I feel pretty comfortable in assuring you that the majority of the general audience doesn't know what the Infinity Gauntlet is. Hell, the vast majority of the general audience, fanboys included, didn't even know who "the purple guy with the big chin" was in the Avenger credits, and had to go Google him.